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Introduction
Exhaust fumes smell bad. In fact, terrible!
But being Carbon Monoxide-rich, it can even suffocate you to death.
Therefore, let’s agree on the point that the exhaust smell you’re smelling around your house right now, is a serious threat. And you have to leave no stone unturned to find its source and fix it up, once and for all.
But how’ll you start the search? Is it just a tiny leak in the flue, or a clogged-up inlet vent? Or something more complicated?
So in this post, I will take you through every possible source of the exhaust fume invasion, and provide you with an actionable solution to each.
Step Zero: Beware of Carbon Monoxide (CO) Suffocation
Before taking care of the exhaust leak(or so), let’s secure our health first.
No matter if you’ve figured out the source of the exhaust smell or not, take measures to calculate the level of CO in the first place. CO comes hand in hand with any exhaust fumes and it can suffocate your breath to death.
First, shut off all the appliances that burn gas or oil (furnace, water heater, etc). Get yourself a Carbon Monoxide Detector(CO monitor) and place it near the possible source of the smell.
Kidde has a convenient CO monitor that shows CO levels in PPM(parts per million). According to that chart, anything above 100 PPM is dangerous for both adults and kids.
- Electrochemical sensor technology detects CO gas
- Easy installation, no wiring needed, detects during a power failure by operating on 2-AA batteries (included)
- Conveniently designed & portable: simple to install on a wall of your home or place on a tabletop
- Green LED indicates power to the smoke detector, while an 85-decibel alarm & a red LED indicates the presence of carbon monoxide
- Peak Level Memory records the last time carbon monoxide was detected or when the unit was last tested
Now, there is a certain detection time that it takes. For example, it will display an alarm of 150PPM after 10-50 minutes of continuous exposure at a Co level of 150PPM. Here’s the full safe carbon monoxide levels chart and scheduling.
What Causes Exhaust Smell in House?
You’ve maybe asked a hundred times “Why do I smell exhaust fumes in my house?”. Guess what, I’ve got 4 possible answers to that, with a solution to each of them.
Take time to go through them in-depth and identify which one has taken place in your home. Here is a quick summary for easy scanning:
Disclaimer: The information provided is intended for general informational and educational purposes only. While we strive to ensure the accuracy and reliability of the content, we do not guarantee its complete correctness. The methods and solutions suggested in this post should be executed with caution and personal judgment.
| Cause | Identifier | Fix |
|---|---|---|
| 1. Faulty Flue Ducting | – Exhaust smell intensifies after cleaning the ducting. – Visible rust, damage, or separation in the ducting upon inspection. | – Clean and repaint rusted areas. – Seal broken parts and leaks. – Replace if beyond repair. |
| 2. Partially Blocked Airflow | – Presence of physical obstructions like bird’s nests or debris in duct caps. – Weak combustion and inefficient system performance due to blocked fresh air inlets. | – Remove any blockages in vents or furnace crown. – Clean intake/exhaust pipes thoroughly. |
| 3. Uninvited Garage Fumes | – Homes with attached garages showing higher levels of benzene or CO. – Visible gaps, holes, or cracks leading from the garage to the home. | – Seal cracks and gaps, especially around ducting and wiring. – Ensure proper ventilation when burning fuels in the garage. |
| 4. Neighborhood Exhaust | – Re-position vents to avoid the direct path of exhaust into the house. <br> – Request neighbors to redirect their exhaust vents if necessary. | – Re-position vents to avoid the direct path of exhaust into the house. – Request neighbors to redirect their exhaust vents if necessary. |
1 of 4: Faulty Flue Ducting
As long as we’re smelling an exhaust smell around, maybe the exhaust air can’t escape properly and backfire to the home. And the frontline reason for that can be Faulty Exhaust ducting.
That makes sense, right?
So, what are we addressing as faults of an exhaust duct that might cause exhaust smoke invasion? According to Angie’s List forum user LCD, they are-
- Rusted through the flue ducting.
- Ducting parts got separated/leaks.
Here’s an identifier that helps you understand if your flue has these three issues or not-
You might have cleaned up the whole ducting right after the exhaust smell had been smelt for the first time. But guess what, the smell became even more after the cleanup.
And that can happen only if the flue has got one of these issues. A clean-up had even enlarged the damage and drew more exhaust fumes in!
The Fixes
Although we’re addressing a faulty flue/exhaust ducting, the three defects have their unique ways of fixing. I’ll talk in-depth about those fixes for the chimney flue.
But before that, let’s figure out what happened to the ducting exactly.
Step 1: Pinpoint the reason
No matter if it’s a rust invasion or separated ducting parts, you need to be certain about it first. Once again, thanks to Angie’s List user LCD for suggesting this method.
You’d need this equipment-
- A strong flashlight.
- A drop light/trouble light.
Now, shut off the entire system and take off the roof cap. Enlighten the ducting from the bottom using the flashlight, and keep inserting a drop light from the top of the ducting.
Make sure that you can see into the duct, and check deeply for the broken/damaged/rusty part of the duct that we’ve talked about.
Once you’ve got an eye on the damage, proceed to the next step.
Step 2: Get off The Rust
Let’s say, you’ve found a rusted flue pipe or portion of the flue that had caused a partial gap/damage within the duct body. How’d you fix that rust in the furnace flue? Or maybe go for a new replacement flue?
Well, as long as it’s not-so-spread rust catch, it’s fixable. Take a look at this 3-step process-
- Use a wire brush to eliminate the loosen-up rusty stuff.
- Use mineral spirit to de-grease the affected part. By that, the oily stain caused by the exhaust fumes will go away.
- Now it’s the stubborn part of the rusty flue pipe. Give a few coats of zinc-rich cold galvanizing spray paint on the entire rust.
- Dry it to touch and place the flue back. Usually, it takes up to 30 minutes to dry.
Done this way, there will be no further rust spread out anytime soon.
Step 3: Fix the Broken Flue Pipe Parts
Sometimes, because of aggressive rust invasion, the flue can be broken or separated between parts. This might be even more likely of a cause why the exhaust fumes are U-turning on their way through the ducting.
Once the rust is taken care of (step 2), seal the broken parts/leaks of it. You can patch up the leaks with small, moldable sealants if they’re small. If they’re large, you might need entire insulation around the damaged area. Wrapping the entire area with roof tape might be good flue duct insulation.
However, if you find the flue beyond repair, you can replace it with a new one. Here’s a step-by-step guide on furnace flue pipe replacement.
2 of 4: Partially Blocked Airflow
An interruption to the entire HVAC airflow can turn the system down. And it all starts with reverse-directing the exhaust fumes into the house.
So what kind of airflow blockage we’re talking about over here? Well, not the one that’s caused by broken, leaky, and rusty flue ducting(as we’ve covered earlier). We’re focusing on external factors that block airflow from the vent.
Some of such scenarios can be:
- Something like a bird’s nest or insects got into the duct cap/furnace cap on the roof. If any such things hang on there (maybe on a screw or so), it might direct the upward exhaust air back into the flue.
- A blockage of the fresh air inlet of your newly installed HVAC devices(water heater, heater, AC, furnace, etc) by dust, birds, bird nests, or insects. This will induce weak combustion and blow out partially burned gas through the system.
The Fix
The simple fix is to get rid of whatever blockage your vents or furnace crown has got blocked with. It can be a bird’s nest, a bird(alive or dead), dust, debris, and other macro-contaminants.
Blockage Type 1: Bird/ Bird Nest in Air Duct
If it’s a bird’s nest or a living bird, beware of reaching any kind of harm to them physically while you’re leading them out. If it’s nested in the chimney, there’s not much to do instead of relocating it nearby.
Blockage Type 2: Dust and Debris
On the other hand, dust and dusty particles can also block the inlet or exhaust up. This happens more with high-efficiency furnaces that’d been kept uncleaned for years. While your home is built new, there also can be construction debris in air ducts.
The good news is, that getting rid of a dusted inlet is easy. All you need to do is follow these steps-
- Step 1: Locate the exit point of your intake/exhaust pipes.
- Step 2: Open up the vent pipe with a screwdriver.
- Step 3: Extract the large-in-size dirt and debris out of it.
- Step 4: Use a brush or soft cloth to remove sticky dirt and debris.
- Step 5: Finally, use air duct cleaning vacuum to clean the entire vent thoroughly.
- Step 6: Check for any further blockage with a wire hanger shaped into a shepherd’s crook.
- Step 7: Close the pipe up with the screwdriver.
3 of 4: Uninvited Garage Fumes in House
A ‘Health Canada’ study found that- houses with attached garages can contain a significant amount of benzene(a gasoline-related pollutant). Even states like Colorado, Minnesota, Alaska, and Lowa had also found houses with such garage-generated CO leaks.
The Fixes
It’s quite hard to stop fumes from finding their way into your home through gaps, leaks, and cracks. Hence, we’ve got a checklist that might give you 99% certainty in this regard-
Seal Garage Cracks on The Ceiling
Do a thorough assessment to find every kind of gaps/holes/leaks/cracks from your garage to the home. This list might include a non-air-tight door between the garage and the home.
If you’ve found any, use supplies like spray foam, putty, caulk, weatherstripping, etc. Use these supplies to seal any penetration caused by ducting, wiring, etc.
Finish The Drywall and Ceiling Well
For newly made homes, it’s often for the ceiling and the drywall to have unfinished joints. As you know, those tiny cracks are enough for the exhaust fumes to find a way into the home.
To fix this up, check the drywall and its joints in-depth if they’re properly sealed with tape and compound. The primer and paint have to be checked for any leaks as well.
Burn Oil or Gas with Care
Exhaust fumes are generated from oil or gas burners, which you have to do now and then in your garage. For reasons, this might intrude and cause an oil burner exhaust smell in the house. The same goes for the gas exhaust smell in the house as well.
For safe play, we’d suggest you run those power tools/engines as close to the doors/windows as possible. Use a separate exhaust vent for that.
4 of 4: It’s Coming from The Neighbors
Although it’s a weak possibility, we would like to check for a closely placed exhaust vent through the wall near the ground level. If the furnace/heater system of your neighbor is large enough, it might get through your air inlets and cause an exhaust smell.
The closer you live to such neighbors, the more likely this is to happen.
The Fix
Simply put, either you or your neighbor need to set the two vents(your neighbor’s exhaust and your inlet) at a distance. A simple request on that might work most of the time.
Asking them to add ducting on top of the exhaust and direct it towards the rooftop might be a good idea, as moving your inlet vents is a way more complicated job.
4 Quick Tips for Eliminating Exhaust Smells in Homes
Don’t want to host the exhaust-like smell in the house over again? Here are some indoor air quality solution tips:
Keep Your Ventilation System Clean
Residential air vents are full of dust, dirt, hair, spider webs, etc. Cleaning them up regularly (once a month) will boost the HVAC system, save you money, and prevent unwanted exhaust fumes from getting into the house.
Use tools like a heavy-duty vacuum cleaner, cleaning brush, wire brush, broom, etc as a cleaning tool. Make sure the vacuum has a long hose to reach deep into the vents. This will bring out the molds and mildew buildups inside the air ducts.
Also, clean the grills in your ceiling regularly.
Don’t Keep the Inlet and Exhaust Close
We’ve not seen many people do so, but it’s quite stupid to keep your air inlet and exhaust outlets close to each other. Although inlet pipes face downwards and the exhaust faces upward, but being close to each other, the inlet can such up the exhaust gases back into the home.
Therefore, keep them at a distance of at least 5 feet. Keep the areas nearby clutter-free(plants, debris, etc).
Bird-proof the Furnace Vent Cap/Chimney Cap
Apart from rainproofing the crow/cap of your roof vent, it’s quite important to protect it not to let the birds/insects get in. You can start by installing a wire mesh into it. And seal it well from the ground insects.
The best solution would be anyway, to get a ready-made furnace cap that checks all of the security features. Otherwise, it won’t be surprising to figure out a dead animal in an air duct once in a while.
Keep Your Air Filter in Good Health
Apart from cleaning the furnace filter regularly, you’re also advised to keep it in check for misplacement or break. Often, due to overuse or unfit filter slots, air filters get displaced or bent. Done so, it will not be able to keep the exhaust fumes and smell away as it’s supposed to be.
So, check for a misfit or damage or clogged-up situation of the furnace filter regularly.
The Verdict
Making sure that you’ve gone through everything we’ve written, we’re sure that you know the sources of the smell of exhaust fumes in the house and how to fix them.
I want to hear your questions or solutions. Please ask below in the comments form.
HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.
I live in a three story home, who would I contact to check the glue for blockage?
First of all I don’t have a gas furnace and I don’t smell the exhaust smell when the furnace is on I smell it when I’m laying in bed and I don’t smell it outside so I have no clue where the smell is coming from but it’s very strong sometimes even makes me cough, do you have any suggestions
Why do I smell exhaust fumes in my lounge every time a car goes past? It never used to happen until after my neighbours’ house burned down. I live in a semi-detached . I was out of my house for a year and I started noticing it soon after I returned. It seems to have got worse during the summer months
My front living room often smells of exhaust. It doesn’t smell in any other room. There are no gas appliances in the room. There is a chimney (no fire or anything installed). But it doesn’t smell outside the house. There’s isn’t a close neighbour on that side of the house either. And im nowhere near a road, im actually down a pathway and can’t even park outside my house…. Its driving me nuts!